Hi 2 weeks ago my 7yo daughter bumped her back, just below ribs, on the bottom of a rather steep slide at a soft play center. At the time she cried for about 5 mins, but we could see nothing, and she still had (and has) full motion, so she ran off and continued to play for another 2 hours with no complaint. 2 weeks later there is a lump in the place where she banged her spine, and she says it is sore when she jumps (but not so much that it stops her doing it). How concerned should i be?