Marks on two year old's lower back, red bumps on his chest area and arms?

I have a two year old son, He is still in diaper's (we're working on potty training him at the moment but he still uses diapers) anyway..he has what look like scratch marks from his diaper on his lower back, We're not sure how or when they happened we just noticed them when we changed him..what could this be from? Also, He has little redish bumps on his arms on chest area..what could that be? It does resemble a sort of rash and we have been putting rash cream on it. He has a doctor's appointment Tuesday but I just wanted your opinion on what could be causing the bumps and scratch marks.