| This answer is opinion-based.|
Due to lack of canonical information in the franchise, there is no definite answer to this question.
When Tigress said that she "feel[s] nothing," she likely didn't mean it literally—she was probably just tersely stating how high her tolerance towards physical pain is, as she had stated to Po after he hurt himself punching her paw. This implies that while he can hurt himself by hitting something hard, Tigress' training had made her paws so tolerable to impacts that she isn't hurt in the slightest. So far, this ability to "feel nothing" has only been demonstrated through physical blows, not through gentle touches like when Po held her paw, or when he lightly tapped her on the arm.
- This question is a follow-up to "What woke Tigress up when Po swam up to her?"