I now have a sinus infection after having my lower right wisdom tooth extracted a few weeks ago. Is this a complication?

Not related. The maxillary sinus sits right above the roots of maxillary molars and premolars and is not related to lower teeth. See your PCP if concerned.
Not likely. Sinus problems due to dental complications involve the upper teeth. The roots of the upper molars are adjacent to the maxillary sinus in the upper jaw. Your lower teeth are in a completely different bone (mandible) that does not connect to sinuses. .