Hi there. It just means he is scared - most hamsters aren’t keen on a hand in the cage, even when they are tame, but if he ran at your hand it will be fear of an intruder in his territory. The biting could be if your hands smell of food
Testing to see if you’re edible. They can get cage rage if they’re stressed but that seems unlikely in a good sized cage - unless you have been cleaning him out a lot and throwing away his nest and hoard! Too much cleaning out can make them very stressed - it removes all their scent. If you have at least 4 to 6 inch deep substrate you can use a litter tray and spot clean mostly then you don’t need to change the substrate for a long time - I go 2 to 3 months. Their nest and hoard can be left alone unless pee’d in but they hoard might need pruning down a bit from the bottom when you eventually do a substrate change.
Having said all that it is a top opening cage and some hamsters feel scared by things coming from above - like a claw! Being prey animals and a front opening door is a lot better generally fir interaction. Add into that he may have been roughly handled by his previous owners or at some time before that.
If you can get a cage with a front opening door that would be a good start to taming, along with plenty of enrichment in the cage - variety, a nice house, tunnels and chews etc. Plenty of hidey places - so he feels happy. After that you’ll probably need to take it slowly so trust builds. He needs to get familiar with your voice and scent first and you could then try some hand taming out of the cage - eg in a playpen area or dry bathtub. You could wear gloves if worried he may bite.
If he’s had a really bad experience with hands previously it could take a bit of time for him to trust being handled. I had a Robo I never could handle (he didn’t bite but hid and didn’t like being handled) but still had a lot of interaction with him and little chats.
A good cage is probably the Hamster Heaven got a dwarf hamster - if you take out the plastic tunnels and penthouse and just leave the one solid shelf. It’s not too tall a cage and has a lovely big front opening door. I would also suggest getting both an upright wheel and a flying saucer for added enrichment and hidey places like cardboard boxes. You could also scatter feed as they like foraging.
Not sure how long you’ve had him but the first couple of days it is best to completely leave them alone. After that they need a couple of weeks settling in time so during that time don’t do clean outs or move things around in the cage. You can keep talking to him through the bars and offering him a treat through the bars. Unless he shows signs of wanting to come out I would wait that two weeks and just keep talking to him and offering him treats through the bars. After that you could lower a tube into the cage with a smelly treat at the far end (the other end near his house). When he walks into the tube for the treat put both hands over the ends (wear gloves) and lift him out in the tube keeping it level. Don’t jump and drop him if he pushes against your hand. You need a box right next to the cage so you can put the tube down on the box and let him walk out of it. You can then carry him on the box to a playpen area or bath area for taming. They can have completely different behaviour out of the cage than in the cage - in the cage they are territorial.