hamster squeaking

I have a dwarf hamster and he is about 1 and half years old. He has been squeaking during the night multiple times everyday for the past week. He went to the vet three weeks ago because he was squeaking and i checked his body and found a bump on his stomach. the vet said it was likely a cyst and that it was healing at the time and to just observe it. my hamster squeaked less for those two weeks but this week he started squeaking more. The bump appeared but is smaller than usual.

Hello - I do not have enough context to answer this question.  Good Qs for your vet include how did they know that it was just a cyst?  Were they able to drain or sample it?  Were they able to rule out a encysted cancerous lump?  Is your hamsters breathing ok?  And sometimes, 'how confident are you in that answer and is it worth a second opinion?' as many vets, like me, are not hamster specialists.  This sounds like a significant change and may, depending on your vets answers, be something that may need to be investigated further.