To test for DeQuervains syndrome place your thumb of the the affected hand into the the palm and wrap your fingers in a fist around it. Then ulnar deviate your wrist. This is called Finklesteins test and will cause pain if DeQuervains is present.

Possible signs for a fractured scaphoid would involve a fall onto an outstretched hand. You would find tenderness in the anatomical snuffbox (the dip around the base of the thumb).

If you are unsure always be cautious and seek an x-ray. Better to be safe then sorry.