it's difficult to make a diagnosis without knowing exactly where in the elbow you are feeling the pain. it's not normal for a 13 year old to have elbow pain and so I would encourage you to see your dr and get an X-ray. this could simply be an insertional tendinitis
such as golfers or tennis elbow
but there are other problems that affect children's elbows that could only be diagnosed with further tests, for example osteochondritis
if you look up tennis and golfers elbow on the internet and feel that your symptoms and the location of your pain is appropriate for these diagnosis then rest and antinflammatory medication can help. physiotherapy
with modalities such as ultrasound
can also be of benefit.