Found a cut like sore on my inner thigh don't remeber cutting myself what could it be.

Chafing. Sometimes an item of clothing can chafe in one spot and cause a sore. Multiple medical conditions can lead to sores, but if this is the only one, a local effect/cause is likely. If ti fails to get better, or if other sores develop in other areas, please be sure to get his checked by your doctor.
Need more info... Syphilis, herpes, laceration, chafing...It's hard to tell you definitively without unintentionally making you more worried. You are better served by seeing a healthcare professional about this since seeing the sore and understanding the context of your life will yield an answer.