I have pain in the lower left side of my mouth

Hi:
Unfortunatley without an X-ray and photo it is difficult to give you accurate advice.  Please post photo and X-ray of the area.
Best,
Dr. Maddahi

It is not typical to have sinus related pain from a lower tooth. It may be that your bite needs to be adjusted. I would see a dentist that treats TMJ and bite related issues

Hello and thank you for your question. The best way to answer this is with an in-person evaluation, however this is unlikely due to your sinuses. I recommend consulting with a Prosthodontist. A Prosthodontist is a dental specialist who has advanced training in restoring and replacing teeth and can create a customized treatment using the latest techniques in dental crowns.

Typically, a lower tooth won't be confused with sinus issues. Pain to biting pressure could mean a number of things. Without xrays and an exam, it's impossible to say what's going on. It could be inflammation of the nerve due to decay, the root of the tooth could be fractured, or there could be irreparable bone loss around the tooth. I would highly suggest seeing a dentist as soon as possible. If the tooth is infected, you don't want that to get any worse as it could cause serious issues.