Help Honduran Milk Snakehas a bump

[El diablo]

So i got this 8 yr old honduran milksnake named el diablo, i brought him to a local reptile specialty store Underground reptiles to check out some concerns i have. He has a small bump on him that is discolored and underneath the scales it seems, the scales too seem a little warped, they told me it might be because he got pinched or it could be a parasite,they also told me he was pretty skinny and assumed he wasnt eating well, and to watch and see if he gains weight.Shortly after he was fed 2 rat pups which he regurgitated, but im pretty sure i made a mistake of feeding him too much at 1 time even though i was told to feed him that amount. I talked to the guy who i got him from who told me he had the bump for a long while and he had been eating well, which has me concerned for how skinny he is. Overall he is a wonderful snake very very good temperment for a honduran and very pretty, but id still like to hear suggestions on what to do to help or what the bump could be.
Also sorry for bad grammar i needed to write this super quick.