Sounds like the firing pin return spring is broken/missing or the pin is gummed up, did you try a dry cleaner/lube spray to see if you could free up the pin so it retracts on its own? I've never removed just the firing pin, but I think the top frame pin will release the firing pin, whether you can get it back together without a complete R&R I don't know. You could also send it in the H&R for repair, they should cover shipping, give em a call at their toll free number (866)776-9292.
Complete trigger R&R by Perklo info can be found in the FAQs, although he doesn't show firing pin removal since it's not required for a trigger hone.
Tim