As long as you're not allergic at all, then the swelling should go down within a day, maybe 2 at the most. You can use ice to help the swelling and take ibuprofen or tylenol for pain.
It won't hurt you to take benadryl if you're worried about the swelling being too big as long as you're able to take that med.
Since it is on your mouth, watch the swelling closely so that your throat isn't compromised.
Pushing on the site and "worrying" it won't make it go down any faster and can actually lead to bruising since the skin is already stretched, so be sure to leave it alone until it's down.
Also, if it's on the inside of the lip, it's easier to get small cuts from hard chips and other foods etc., since it's swollen, so limit anything that normally irritates your mouth.
Good luck and I hope you feel better soon.
Atleast it wasn't before school pics or a special date!!!