Muscle strain: This is the most common cause of groin pain in young males, often resulting from overuse or trauma to the adductor muscles. The normal blood test results support this diagnosis, as muscle strain typically does not cause abnormal laboratory findings.

Inguinal hernia: Although more common in older adults, inguinal hernias can occur in young males, especially if there is a familial predisposition or history of heavy lifting. Groin pain is a typical symptom, and a normal blood test does not rule out this condition.
Epididymitis: This is an inflammation of the epididymis, usually caused by bacterial infection. It can present with groin pain, but the pain is often more localized to the testicle. Normal blood tests might not be expected in epididymitis, especially if the infection is not severe, but it's still a consideration.
Osteitis pubis: This condition involves inflammation of the pubic bone and surrounding structures, often seen in athletes. It can cause chronic groin pain and might not be associated with abnormal blood tests.

Testicular torsion: Although less likely given the description of "groin pain" rather than "testicular pain," testicular torsion is a medical emergency that requires immediate attention. It can sometimes present with pain referred to the groin. Normal blood tests do not rule out this condition, and any suspicion warrants urgent evaluation.
Appendicitis (with atypical presentation): In rare cases, appendicitis can present with groin pain, especially if the appendix is located in a retrocecal position. While blood tests are often abnormal in appendicitis, early in the course of the disease, they might still be normal.

Avulsion fractures: These are rare injuries where a fragment of bone is pulled away by a tendon or ligament. They can occur in the groin area, especially in athletes, and might not always be associated with abnormal blood tests.
Sportsman's hernia (Gilmore's groin): This condition involves a spectrum of injuries to the groin, including tears of the external oblique aponeurosis, conjoined tendon, and inguinal ligament, without a palpable hernia. It's a rare cause of chronic groin pain in athletes.
Psoas abscess: Although rare, a psoas abscess can cause groin pain due to the proximity of the psoas muscle to the groin area. Normal blood tests might not be expected, as this condition often results from bacterial infection, but it's a possibility, especially if the abscess is small or in its early stages.