I have a hard lump close to or attached to my left testicle?

See your doctor. Testicular lumps can be cancer or benign. You don't want to take a chance of misdiagnosing yourself. Testicular cancer can be extremely aggressive so don't delay. Go see your doctor for a thorough exam. S/he may order an ultrasound to determine if you have a mass inside the testicle, but hopefully it is something benign such as a cyst or varicocele (dilated blood vessels). Good luck!