What exercises should i do if?

well you see i had cancer twice well i had a relapse now im ending my second time around , im in the "maintenance" stage of the treatment and the thing is that i want to get in shape again like i was before this "thing" , so i don't really want to lose weight i just want to get my muscles in shape and make then look hard not fluffy , and the problem is that i have a lot of pain because of the chemo and tingling in the arms and hands i ask my doctor and all he says is" exercise as much as your body allows you too ' but i don't feel comfortable with that answer, can you tell me some exercises to help me lose the man boobs (i don't really have that much but i don't like them ) i would like a flat chest so that and i would also like to get muscles in my arms , thank for all you answers :D