[cypher]

I think you need to try to work out why he bites when he does, if a ham is fairly tame & not a biter then sudden bites are usually caused by a fright, being startled or occasionally mistaking fingers for food but they tend to grow out of that last one quite quickly.
Try to think about what may have scared him when he bit you (sudden noised or movements, other animals around, any changes in his routine, cleaning or play time) & try not to be too nervous. I know that's easy to say & bites can be really painful but if you are nervous he will pick up on it & it can just make things worse.
If he only bites in the cage then try using a ball or jar or tube (anything he's happy to climb into) to get him out & take him to a safe area where you can handle him.