My 5 year old son was playing in his room and fell face first and hit his chest should I take him in or should I take him in to the doc?

Go with your gut. Kids fall a lot, and you don't need to head to the doc every time. Sometimes the "mechanism" is enough - like falling off the roof. But mostly it depends on whether he's having problems. For head/face trauma that would mean bleeding, passing out (even briefly), vomiting, bad headache, or blurry vision. Falling on his chest should be ok unless there's a lot of pain or trouble breathing.
CHEST TRAUMA. Depending on the trauma, does he complain of pain, any discoloration or swelling? If he has symptoms, then have him checked.