I am quite concerned as for the last 3 months I have had a tiny lump on the skin of the shaft of my penis. It is hard and just looks like a spot with a white head. I thought nothing of it until I have just noticed another 2 now starting to form around the same area. What do you think it could be?

There are too many possibilities to guess.

You need to see a doctor.

Could be a pimple type spot don't pop it try to wash there gently, if it gets worse see a doctor might be just be a cyst.

It it on the outside of penis or under foreskin anyway see someone soon if it gets sore.