Can I use my penicillin even if it has expired?

Usually, we do not recommend using expired products since companies cannot guarantee the quality of the product past the expiration date due to lack of research. Some people will tell you that at worst, an expired product would be less effective... maybe, but it happens sometimes that the product becomes harmful. Moreover, if your product has been kept in the light and in the bathroom (a lot of humidity), the degradation is faster. Also, the reason for your dental pain may not be an abces. For the moment, I suggest you take painkillers (ex. Tylenol and especially Advil if you are allowed) and go to your dentist for an emergency appointment. Hoping to have answered your question