Here is a piece i found online about cooking bones... it's from a Raw Diet website...questions and answers...RMB stands for Raw Meat Bones...and here is the question...

Can I use my microwave for thawing RMBs?

When using a microwave to thaw RMBs, you must be extremely careful, as the microwave can begin to cook the food from the inside (the bones) out. Thawing RMBs in the microwave is NOT the recommended method. NEVER, EVER give your dog a cooked bone, as it can splinter and cause severe internal complications. The safest method of thawing is room temperature or, if you're in a bit of a hurry, soak the RMBs in cold water in the kitchen sink.

here is the link where i found it...

http://www.njboxers.com/faqs.htm#micro

I wouldnt worry too much, i just wouldnt do it again...i wasnt aware about not giving cooked bones until my breeder told me about and then i researched it...anyway, i wouldnt worry, i am sure your dog chewed it well...just keep an eye on the poops...

Robyn