As the others say - they need separating now. The next fight could leave serious maiming or death - this has happened to a lot of people. With serious maiming it could mean a lot of vet treatment or even having a hamster put to sleep. If you have a storage bin just pop one of them in that for now - even if it isn't made into a bin cage yet - with some substrate and toys/wheel. It doesn't have to be expensive getting a second cage and you could get something that will stack on top of or under your existing cage (eg a bin cage). The Samla bin from Ikea is popular. The cheapest new one to buy that I know is the Standard Duna multy which would make a good cage for a single dwarf hamster. You can get it next day delivery from here and it costs about £33. Bar spacing is small enough for a robo and they are a popular style of tank cage for dwarf hamsters - less diy than a bin cage. Just thinking it might be a quick solution.
Cage Duna Multy
If you don't have a plastic storage bin, then maybe try and find a piece of wood to split the cage overnight - but a determined hamster may push it over or get round the edges if it's not wedged tight. I would suggest removing the injured one and leaving the other one in the current cage.