Had blood clot in right leg on blood thinner, tonite had sharpe pain top of right hip and lower right side of tummy. What could b the cause of pain?

DId it go away? If the pain went away within an hour or so, it's unlikely to be anything serious. If the pain persists, or gets worse, then it could be abnormal bleeding within your abdominal wall, or within your abdominal cavity. These would be reasons to seek prompt medical attention, in case your blood thinner medication needs to be adjusted.
Need more info. If you are taking therapeutic doses of blood thinners then you should be protected from further thrombosis. It is likely that you are more aware of normal aches and pains after having a deep vein thrombosis. However, if the pains continue they may need further evaluation.