Large Bump On Back, White Seeds Coming Out, Has Odor
Thanks for writing in.
It looks like you are suffering from a sebaceous cyst. These cysts arise from a blocked hair follicle. Once the follicle gets blocks, secretions get accumulated and a lump gets formed.
If the lump has started hurting or looks red, you would need to see your physician who can drain it for you. Else, warm compresses ( take a cloth and soak in hot water. Let it stay there for a while and then squeeze to drain the water. Check the temperature on your hand and then apply on your back) are all what is required. This will help drain the cyst.
To prevent these in the future, make sure you scrub your back with a loofah or use an exfoliator to scrub your back while bathing to remove the dead cells.
Hope that helps. Let me know if you have any more concerns.
Regards