I'm taking it you are either a 2017 or 2016 player....that being the case, you certainly have more time on your side than a 2015 or 2014 trying to get committed somewhere. Either way, you would not want to throw until you have a diagnosis of what is wrong.
Elbow injuries are tricky, and even many ortho Dr.s miss on this one...best if you have access to one that specializes in elbows, and even throwing injuries. Now here is the likely scenario as it relates to today's insurance, etc....typically the ortho will take an x-ray to rule out skeletal issues, which is less likely what you have going on here, but they still will rule that out. They will also see if at 15 years of age, your growth plates have closed. If the x-ray turns out well, then the likely protocal will be a period of rest (no throwing) followed by a detailed throwing regiment geared towards working up the amount of throws, distance, intensity, etc. (could be the short interval throwing program by Dr. James Andrews - you can research online).
If you can not get through the rest period, and the throwing program without pain, then you start over again, and normally only then will they perform the MRI. Depending on your insurance / ability to pay for an MRI, you could take a different approach, and tell the Dr. your elbow "REALLY" hurts, and ask for the MRI now. Then you can have the peace of mind of knowing exactly what soft tissue damage you have, if any.....that would be my recommendation if you are experiencing serious pain when you throw, or if you elbow hurts to the touch even when not throwing, especially if the pain is very localized in the typical UCL area....
my .02 cents