I have undergone an extraction for my lower, first pre-molar.an inferior alveolar nerve block was given to me but since, there's pain at the injection site and reduced mouth opening. what should i do?

Give it time: I assume the procedure was just recently completed. You should give it some time for the soreness should go away, check with the dentist if you are still having trouble with the area in a few days. Message your jaw and moist heat may also help.

Common: Pain at the injection site is common as there can be some bruising when an injection is given. You will also have pain at the extraction site. This will heal over a few days. For now, soft diet, ibuprophen for pain and ice packs will help. Please call your dentist if you have concerns or if things do not improve quickly.

Not uncommon: Occasionally, for this type of injection, the muscles may go into spasm and there is also some local inflammation which produces the symptoms that you describe. Take some otc pain medication such as advil, motrin, aleve (naproxen) or what you normally take for a headache. Warm rinses and external moist heat may help as well. This should pass shortly. Call your own dentist if still concerned.