Hi, Thanks for query.
It seems that you might have some blood collection on left buttock,called hematoma
There is less chance of having fracture
as you can walk.
Pain you got might be due to strain over the muscle.
Take antibiotic and anti inflammatory medicine for 3-5 days.
If pain and difficulty in walking persisted,go for x ray
of the part to rule out any fracture at hip or thigh.
Ok and bye.