Can you have receding gums in only one tooth? how is this treated & could it cause infection in tooth & cause need for root canal??

Yes... and No: Yes, you can have receding gingiva in just one tooth. And it will not cause an infection since bacteria have not entered the pulp chamber. Can trauma cause the nerve to become non-vital? Yes. Can recession make the tooth become so sensitive that root canal therapy is necessary? Sometimes. Your dentist needs to examine all of these possibilities.