What is the most sensitive/painful body part to get a tattoo?

Most and least painful spots to get the tattoo 

Most of the data on tattoos and pain is anecdotal, but some general rules apply. The most painful places to get tattooed are typically bony and have very little fat covering them.

The most painful areas for all people include the: 

Feet, Ribs, Spine, Stomach, Fingers

Chest, Knee, Elbow, Shin, Neck, Groin

Head and face , The bony part of the ankle

Less painful areas to get tattooed include parts of the body with thicker skin and more fat, including the: 

Forearm , Hands, Shoulder, Parts of the back 

Back of arm , Stomach , Outer arm , Outer thigh 

How bad do tattoos hurt?

There's no one-size-fits-all answer when it comes to how much pain you'll feel when getting tattooed.

Long periods of irritation and tenderness are what make you feel any discomfort, the sensation of a tattoo needle is very dull compared to a syringe [and needle], it isn't the needle that causes discomfort as much as it is prolonged tenderness of being tattooed.

Importantly, different people will report varying experiences of pain based on their individual nervous systems and pain thresholds. Other factors that could affect pain during tattooing include:

Age: Studies suggest aging decreases your pain sensitivity, meaning elderly people might experience less pain when getting tattooed. Researchers have yet to determine why this happens but note that the size of parts of the brain that process pain decreases with age. 

Sex: People who are biologically female are more likely to experience greater pain intensity, a lower pain threshold, and a lower tolerance for induced pain compared to people who are biologically male. However, research is still emerging. 

Psychological expectations: If you go into a tattoo expecting it to be an excruciating experience, this might affect how much pain you actually feel. Studies suggest that people who feel anxious about and "catastrophize" pain before a procedure often experience higher levels of pain intensity and distress than people with "neutral" pain expectations.