Noticed hard lump mid lower leg,top of shin today size of large marble.knee pain too but thats not uncommon.tender to touch.no recent injuries but i have fibrous dysplacia in skull,could this be same on leg now?i was told it only occurs in1 location?

By Mayo clinic: "in most cases, fibrous dysplasia occurs at a single site in one bone, but can occur at multiple sites in multiple bones. Single bone involvement usually occurs in adolescents and young adults". You should see you doctor for a leg X-ray if the skin over the lump is normal. If the skin is abnormal, fibrous dysplasia is less likely.