What can i do for new onset aphtous ulcers in the lower lip that are really painful, 8mm in diameter well demarcated erythema around?

Two suggestions-: There are many otc medications that you can get at your local drug store that will offer some relief. Ask your pharmacist from what they have available what he\she thinks is best. A better option would be to see a dentist who has other medications and treatments either in his\her office or can prescribe for you.

Laser: If your dentist has a soft tissue laser, he or she can 'zap' the ulcer at a low setting that will immediately eliminate or significantly reduce the discomfort. There are also over the counter products to coat the ulcers and help them heal less painfully. Use of colgate total toothpaste has anecdotally been associated with fewer apthous ulcers, likely due to its antibacterial properties.