Sore, swollen tongue only on back left side. can you think of any possible causes - did i bite my tongue? how long will it take to get better? are there treatment to help expedite this?

Yes, Perhaps, varies: Yes, you might have bitten your tongue, or from irritation from sharp teeth, or canker sore or a host of other causes. Most of these types of situations will be gone in 2-14 days. Salt water might help, many OTC medications at the local pharmacy. You can either consult a dentist now, or wait it out. If not gone in 2 weeks, you should consult with a dentist as some situations require prof. care!

Quite common: The tongue biting during sleep has been reported as a common symptom in association with night bruxism. The custom night guard can be designed and fabricated by your dentist to prevent jaw closings during sleep, therefore preventing tongue injury.