How can I fix my bottom lip? (Photo)

You must have injured the marginal mandibular nerve on your left side. I have seen this in patients who have had dental blocks, and there are other reasons why this might happen.  Sometimes this problem can improve a little with time.If you have not already done so, your first course of action should be to determine the cause by consulting an ENT doctor or neurologist. If you know the cause and it does not require further evaluation or treatment, you could consider a small amount of one of the botulinum toxins, such as Dysport or Botox, to the DAO muscle on your right side only.  This will improve the symmetry of your lower lip but temporarily you will not be able to pull down the right side of your lower lip, just as right now you cannot pull down the left side.i would love to hear how you fare.

You have a marginal mandibular nerve paralysis in the left side. (the left lower lip is raised up higher because no working muscle is pulling it down like the normal right side.) Such lower lip problems are usually treated by a depressor anguli oris myectomy (to help raise the normal right side) and a left lower lip reduction. You will not likely get perfect symmetry between the two sides but the discrepancy will become less apparent.

The one half of the lower lip is not moving, the cause was not mentioned, if it is trauma, no reason, surgery? you need  to see a neurologist and a plastic surgeon