I Have A Sore Place Under My Tongue On The

I have a sore place under my tongue on the left side. It seems to be infected and I may have bitten myself or hit my gum with my finger nail. I have an appt. on Friday but until then my Dr. has said to use Mylanta. To put it on the sore place with a q-tip. Is this the right thing to do. I have a total knee replacement and usually have to take antibiotics when I go to the dentist.