I've had swollen, hard and painless lymph nodes with a huge bulge in my inguinal area for years - could this be lymphoma, a cyst or a hernia?

Need to examine: It is not feasible to provide meaningful advice without examining you. What you described does not sound urgent, but it would be prudent to see your doctor for an evaluation. For good health - Have a diet rich in fresh vegetables, fruits, whole grains, milk and milk products, nuts, beans, legumes, lentils and small amounts of lean meats. Avoid saturated fats. Exercise at least 150 minutes/week and increase the intensity of exercise gradually. Do not use tobacco, alcohol, weed or street drugs in any form. Practice safe sex. Get HPV vaccine.