What was found
FLT 8552 - RETURN TO POINT OF DEPARTURE. AFTER TAKEOFF CHECK-LIST HAD BEEN COMPLETED DURING CLIMB-OUT, FIRST OFFICER NOTICED THE NOSE GEAR UNSAFE LIGHT ON AND OFF. LANDING GEAR LEVER IN UP POSITION. REFERRED TO ABNORMAL CHECK-LIST, FOUND NO SOLUTION. RECYCLED GEAR DOWN 3 GREEN LIGHTS ON, THEN BROUGHT GEAR LEVER UP, GEAR RETRACTED WITH THE NOSE UNSAFE LIGHT INTERMITTENT. RETURNED TO LANAI. DIRTY PROXIMITY SWITCH SENSORS ON NOSE GEAR WOW TARGET.