Does his foot hurt where he has the rash? Did you know you can get Shingles on one foot? It hurts like crazy and if it isn't treated, it can last for years. Does it tingle? Itch? - the info about tumors/lipomas from mkh9 is correct.
Wishing you the best
Hi, What is the lump on the side of your boyfriends body feel like. Is it hard and stuck to the body or is it spongy and pressed in like it is filled with water? Does it hurt? It could be a lipoma which a benign fatty cyst growth.. But if it is hard and solid then it could be a benign or not tumor. Either way he should get it checked out by a doctor. It can also be a cyst. So, most of things are benign. Does he feel very fatigued? Lost a lot of weight? If not he is probably ok. I don't think the rash on the foot if related. It could be that the hydrocortisone cream made it worse because it is a bacterial infection or if it is fungal the fungus was resistant to the fungal treatment used . Best to go see a doctor and stop self medicating and see what is going on.
Hope this helps.