If you shake the plant do you see any tiny, tiny white bugs flying around? It may be damage from white fly nymphs. Insecticidal soap is used to control them and is safe for plants that will be consumed.
My second thought is some sort of virus/bacteria inside the leaf but not much you can do about that.
I suggest to treat for whiteflies (spray both sides of the leaves) and see if that helps. The bumps will probably stay on the older leaves so check new leaves and see if the bumps continue to happen.