Hey Justin i recently been experiencing "Repetitive Strain Injury" in my left hand. This was due to chord practice.
I was wondering if someone plays guitar the whole day, how long should he rest before playing chords again?
Thanks a million Justin! 
As sophiehiker says,a Doctor might best answer that.....
I did something very similar to myself,a few months back....Got sore so on the top of my hand right at the wrist,from chord changes,that it was 5 days before I could pick up a guitar again...
Having two sisters in law that are LPNs,I went to one of them,rather than a Doc...Experienced advice for free....

...She was of the opinion that I'd given myself a mild,(still painful) case of tendonitus,and to treat it the same as the two "officially" diagnosed cases I'd had,(work related) were treated...
You should stop NOW and recover,whether that be 2 days or 2 weeks....
I pushed through right up til when the pain literally MADE me stop.....Now,some 3 months later,although I've learned lots of new stuff,I am just now getting back to being able to practice for comparable lengths of time as before I hurt myself.....
Be very careful...
