If the outer case of the pump has had a ding, then it may have bent it away from the large O-ring round the outside of the pump.
If it's an old type with the banjo fitting on the rear or the newer one with the high pressure fitting on the top you will need ta remove both in order ta remove the back of the pump ta check the O-ring, apart from replacing the high pressure fitting seals "copper or O-ring" that's about all you can service on them.
Good luck with it.
Jed