It could be a number of things in addition to what you've mentioned. I take an old ball that you can experiment with and change span and/or pitches and throw it awhile to see.
Things like that don't get better by bowling, however, it usually takes rest, ice, and anti-inflammatory drugs like ibuprofen or naproxen sodium before they calm down. Good luck.
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notclay
Lane Carter, Strike Zone Pro Shops - Salt Lake City, Utah
"The problem is no that there are problems. The problem is expecting otherwise and thinking that having problems is a problem." ~ Theodore Rubin