I'm 62 yrs old and have started having discomfort in my left knee when I kneel that feels like a carpet burn, should I be concerned?

Probably not. If you describe the location it would help. Infrapatellar bursitis will frequently complain of pain and swelling in the front knee below the patella that can radiate below the knee often, is causes severe pain with kneeling or walking down stairs. Common symptoms of itbs ileotibial band syndrome (a different problem), are burning pain in the outside part of the knee. Both do well with treatment.
Yes. It is probably the beginning of osteoarthritis. Exercise your knees. Apply warm water bottle around the knee. You can take Motrin over the counter for pain. You can take glucosamine / chondrotin sulfate twice a day. This is non prescription. Please see orthopedic surgeon for cortisone or synvisc (hylan g-f 20) injections if it remains symptomatic.