I'm experiencing bit of pain in my left breast from few weeks. The pain reaches out till underarm however it's not a constant pain. I delivered a baby last year c section but never did breastfeeding due to low supply. I don't know whether it is related anyhow to this. There is no nipple discharge or any kind of lump observed by me in the breast. What can be the possible reason?

This is because of a blocked milk duct in your breast. Because of lack of active breast feeding, the milk ducts tend to get blocked, causing excruciating pain and turning out to be cystic lumps in future.

Hot compresses, hot oil massage, hot showers and nursing help but only if you are still breastfeeding. But since you haven’t breastfed in almost a year, I would suggest visiting your OBGYN and get advice over surgical exploration of the breast and unclogging the milk ducts.