I have been dealing with, for over a year, a tinglng feeling under my skin of my left breast. I also feel a tighting of muscles underneath in lung?

Breast exam? Have you had a breast exam or mammogram? I would recommend this to make sure there is nothing worrisome going on. If that is normal, you may be having spasm of your pectoral muscles. Try massage, alternating ice and heat, and anti-inflammatories like ibuprofen.
Thoracic Disc ? Given the Nature and duration of your symptoms I would be concerned with arthritis , osteoporosis or herniation of a disc in the thoracic region. T4-6. You need to be examined have labs checked. Thoracic spine X-ray and thoracic MRI if indicated. Also a mammogram and potential breast ultrasound to rule out intrinsic breast disease.
Exam. If this is left sided and you are at risk of heart disease it could be that. However, only way to know for sure what the issue is to see your physician for at least a breast exam.