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Most probably it is gynecomastia as it is common in young age and may cause pain,
Although, breast cancer is rare in males, it is more aggressive with rapid growth and spread.
I suggest that you take painkillers and send me a photo of the red lump
Also if you have noticed any swellings in the armpits please tell me.
In general, you should not worry, but be a little cautious.
For more information consult a general medicine physician online --> https://www.icliniq.com/ask-a-doctor-online/general-medicine-physician