What's a simple, cheap treatment for my osgood schlatter disease?

None: Osgood schlatter will resolve on its own. You can take Ibuprofen or Acetaminophen for the pain, and apply ice after activities that cause pain.

Avoidence: Avoiding the offending activity, ice after use, tylenol (acetaminophen). Some times young adults13-14 have @ take a vacation from competetive sports 2-4 mos @ allow it to quiet down. Avoid loading the knee as in jumping, running esp inclines & declines more so. It is self limiting and stops when growth plates close. Pain goes away lump @ tib yubercal stays as a reminder oo what you had.