What Causes Swelling And Pain In Testicle With A Lump?

Swollen, red, painful left testicle. Small lump at top. Some burning. When I stand it pulls and pain in very low abdominal area. No pain when I urinate. No discharge or blood what so ever. No fever or chills. No trauma. I am 52 y.o. Recently was in Belize two weeks back.