asher362 says:

Since you’ve been cleaning your mouth out for a few days, your lip may be getting tired of the process. This plus the rubbing from your hoop could make a little sore spot on the inside of your lip.
To help, make sure you’re not messing with the jewlery or the sore spot. Its really easy to get into the habit of poking a sore spot in your mouth with your tongue, but DON’T. Rubbing will just make it worse. Leave the little spot alone. If your hoop fits properly it should settle down in a couple of days if you leave the area to recover.
You’ll also find that if you switch to a stud in the future that it will rub a different shaped little cup for itself to sit in. If you wear the stud for a while, your lip will have to get used to your hoop over again. It won’t be as sore as this time, but you may notice it.
If you think your rinsing is getting on your lip’s nerves, stick to the sea salt mix. Make sure your solution isn’t too concentrated so it doesn’t aggravate your mouth. You can also try Biotene which is a brand of non-alcoholic mouthwash that works through enzymes.
If your lip isnt feeling better in a couple more days, have your piercer look at it, but more than likely you’re fine. Keep cleaning and leave it to heal itself.

cher-rol says:

Ok well I dont recommend using the mouth wash and stuff. That is for tongue piercings and that will just annoy the piercing. What you want to do is go out and buy a thing of Lens Plus Sterile saline solution and also cue tips. This might sound weird but this cleans the inside and outside. Poor some of the Lens Plus on the cue tip and then on the inside, move it in to the outside of your lip. And for the outside of your lip move it aways from your piercing. You will want to do this for about 3 weeks or less and anytime it bothers you.
I have my lip pierced and I asked my doctor about the healing process and he says that Lens Plus works the best.