It's my 4th week of non-displaced scaphoid fracture cast, still having tenderness in my palm and thumb. Does it healing No surgery Cast is for 6 week?

Scaphoid fractures. Can take longer than 6 weeks to heal. The cast, if that is the treatment used, can be discontinued only when there is certainty as to the healing. This can take 8 weeks or more and must be verified by new xrays but a times one needs to check healing with advancd studies such as CT scan. A partially healed scaphoid can lead to other problems, non union, pain re injury so patience is important.
Fracture. These fractures take some time to heal. 6 weeks in a cast usually is suffice but pain can persist for awhile after cast is off. Good luck to you. Hope this helps.
Tenderness. First of all, is the tenderness you are experiencing less than when you first had the fracture or worse? If worse, you should follow up with the doctor who saw you in the beginning for a redo x-ray as soon as possible. Does your fingertips have sensation to them or are they painful? If the latter, definitely see that doctor ASAP for compartment syndrome.