Brief answer....your description suggests it to be a sebaceous cyst but you need to consult a doctor for examination.
Detailed answer....
Hello,
Thanks for the query.
I have read your query and understand your concern.
Basically there are two types of solid swellings on scrotum.
One which is present on the surface of scrotum and other type which is present inside scrotum.
If it is on surface ,then most likely it is sebaceous cyst which is not harmful and can be left as such. Proper treatment of sebaceous treatment is,however a surgical removal if it is causing pain or getting infected.
I would advise you to consult a doctor for visual inspection and examination.
If he suspects that swelling is inside the scrotum,then you would need an ultrasound of scrotum for exact diagnosis.
Swellings inside scrotum can be spermatocele or varicocele or hydrocele etc
I hope it helps,however you are most welcome to revert to me for any further query.
Best of luck 
Thanks

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