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Your symptoms appear to be due to mild scrotal / testicular inflammation, and the causes can include mild unrecognised trauma or testicular engorgement as a result of sexual excitement.
Hence you can try to relieve it with OTC medications like acetaminophen (Tylenol) or ibuprofen (Advil, Motrin). Wearing supportive underwear and avoiding strenuous activity is also important.
Conditions like - infections (orchitis), hydrocele,Varicocele - present with enlargement of the testicles as well as variable amount of pain.
Conditions like Testicular torsion appear with severe excruciating pain and severe redness of the testicle. This is a medical emergency which needs immediate surgical intervention.
If you have a sense of vibration in your testicles, and they are warm, red and heavier, then it could be a sign of varicocele. This is a condition where the testicular veins are dilated. This condition needs prompt treatment as well.
Hence it would be recommended that you should consult with your doctor or the ER at the earliest.
I hope this helps.