Why does the muscle left of my lumbar spine heart? the pain is like a pintch and tight feeling. cures? treatments?

Sprain/strain: At your age, the most common reason for paraspinal muscle pain would be sprain/strain. This can happen even if you don't recall the exact injury. Conservative treatment including progressive activity, anti-inflammatory meds, physical therapy, ice and/or heat, and topical over the counter treatments such as aspercreme should help.