How to get rid of a boil with just OTC medicines?

Boils. Apply warm compresses and soak the boil in warm water. This will decrease the pain and help draw the pus to the surface. Once the boil comes to a head, it will burst with repeated soakings. This usually occurs within 10 days of its appearance. You can make a warm compress by soaking a wash cloth in warm water and squeezing out the excess moisture. See your doctor if not improved.
Hot soaks. Warm wet pads place over the boil will allow it to come to a head, break open and drain. Do not squeeze it. That may help to put bacteria into your blood stream. If this does not help to resolve the issue, you may need antibiotics. Be careful with otc remedies other than this because many are unregulated and may be harmful either directly or by inhibiting the use of appropriate treatment.