I found a lump???

hi i found a small like pebble marble like lump in my right i went to the doctors and they said it is fine but recently i have had some sharp pains in the and also she said it moves so that is a good sign but now it doesnt move if you know what i mean! there is just something telling me its not right. but i fell like an idiot going back to the doctors should i go back or not?