I have ear infection in left ear & tooth ache on left side, what to do for treatment?

Time for visit. Tooth pain can generate phantom ear pain and vice versa. If your discomfort is not relieved by simple anti-inflammatory meds like Ibuprofen in a day or two, an office visit to your pcp or dentist or both may be needed to sort it out.
See MD/DO first. An upper posterior tooth's roots are into or near the sinus cavity, and an ear infection can create some pain with the tooth/teeth. If you know you definitely have an infection, then an md/do is definitely the first step. The question is also whether the tooth had pain first or vice versa.