Are the sores very painful, puss filled, swollen, and have they grown over time? If so he COULD have a staph skin infection, or worse a staph blood infection (especially as the sores all over the place from the sounds of it). These can result from IV drug use.
How long has he had these? Do you know if he uses sterile needles and if he cleans his skin with alcohol before and after injecting?
If not, and if the sores have been around for a while, I suggest he see a dr as if it IS a staph infection there could be scarring and regardless he will need antibiotics to treat it.