One possibility is an enlarged vein valve. That would be a soft lump right on the vein. Another possibility is blood blisters, like this one. If they are flat, a possibility is petichiae, which is the result of blood leaking into the skin. They are usually smaller than pea size, though. This article has information and pictures on petichiae.
It's really difficult to tell from here, and I'm afraid a visit to the doctor may be unavoidable (you should do that with petichiae anyway, because it can have causes that need treatment). I don't want to alarm you further, but some rare cancers can start as purplish spots, so getting a doctor to look at them is a good idea to exclude that possibility.