Back pain can be because of many different causes. Considering your history of taking pepper for piles (which is not a recommended therapy) I'd expect it to be a referred pain due to gastritis (stomach irritation).
Next Steps
Stop taking pepper and start a course of antacids. I would suggest any of the over the counter PPIs, Pantoprazole, Esomeprazole, etc
Health Tips
If pain does not subside, further evaluation may be necessary.
A better recommendation could be made with a better, more elaborate personal consultation