A small lump has developed on my back about an inch below my armpit (right hand side). it isn't painful unless i apply pressure, it is skin toned...

Skin lesion: There are several possible causes of a slightly tender lump including cyst and lipoma - these are harmless. If it enlarges further or becomes more painful see your doctor, as your description could also be of skin cancer or an early abscess.

Lump below armpit: May be lymph node cysts, infection. Since it is near the axilla ( arm pit) would have it checked out and also have a mammogram( the LN of the armpit drain the breast) May resolve with antibiotics but still need evaluation. f/u/ w/ doc this week