if you have pain you should go and get it checked by a doctor immediately.
If you are not able to see your doctor for whatever reason, I suggest that you bathe in salty water and apply natural set yogurt to your bruised area.
The salty bath is very healing - you can use Epsom Salts which can be purchased on line or from the pharmacy. 1-2 cupsfuls to a bath is what is recommended on the packet.
The natural set yogurt will help to cool down and settle down the inflammation and bruising.
Don't use soap to wash down below, this dries the skin. Non perfumed soaps and soaps with pH level like our skin is fine.
If you do notice that you begin to feel pain when you urinate or it stings, or a discomfort in the lower belly, then that would mean that you are likely to have a bladder infection called Cystitis. You doctor would give the right antibiotic for this. At home you need to drink plenty of water throughout the day.
A bruise is a bruise and it will go away. If it is uncomfortable, you can apply cold packs. That will help with the swelling. It will get better in a few days. Good luck.