Why would the muscell under my tongue swell up mainly the left side the under my tongue muscels swelled up mainly left sife feels like even pimples under but not on tongue

Many : Many possibilities. Have you been to a dentist to have your teeth examined for a possible infection? Swelling under the tongue is very, vary dangerous. It can start to spread and swell rapidly, lifting your tongue, obstructing your airway, and making it impossible to breathe. Please have it evaluated and treated immediately.

Swelling : Swelling under the tongue caused by a deep infection can be very dangerous. Luckily it is rare. The common name for that problem is ludwig's angina (i have no idea who ludwig was). It this were your problem, you would be extremely sick with high fevers. I think that your problem woudl most likely be some type of inflammation of the salivay glands under the tongue, maybe due to trauma or dental issues. We also cannot rule-out tumor (also rare). If things get worse, you should see a dentist or doctor. Some thinkgs that may help narrow down the possibilities would be knowing if it hurts, how long is it there, are there any other symptoms.