For home care you can use a warm/hot damp compress on the area to help it stay open and drain of infection. This will also stimulate blood circulation to help fight infection. This may also help the spot break open and drain.If it does, ou can clean the area with Betadine iodine solution, chlorhexiderm solution, sterile saline, or 3% hydrogen peroxide. Then apply Neosporin or Triple Antibiotic ointment to the wound or any scabbed over areas. Keep the dog from licking the ointment off. It won't hurt the dog if it gets licked but it does better on the wound than on the tongue. A bit of peanut butter on the roof of the mouth can keep the tongue busy while ointment soaks in.I'd do this 2-4 times a day and if you see no improvement or the infection seems to spread get to a vet for oral antibiotics (which would be a good choice anyhow with an infected injury).
But if this looks like a big red wart with a rough surface this may be a histiocytoma which you can read about here
it often looks like a blob of bubblegum stuck on the skin and usualy resolves on its own.Hope this helps you!
The easiest solution may be an in person look by your vet to see if its an infection or a histiocytoma.
If the surface is all wrinkled and wart like then its not likely an abscess. Usually those look a bit smooth and more like a pimple in giant size.
But if you are not sure what it is then an in person vet exam is your next best step.