And no, that does not mean that he doesn’t have enough veins.
It is a non-life threatening condition that is apparently common with older individuals. Which means there is no need to panic, at least according to a statement by the White House.

What is Chronic Venous Insufficiency
Chronic Venous Insufficiency (CVI) happens when the veins in one’s legs don’t efficiently pump blood back to the heart due to being damaged. This results in blood pooling in leg veins, according to the Cleveland Clinic.

Dr. Barbabella also addressed recent photos of the president’s hands which “have shown minor bruising on the back.”

“This is consistent with minor soft tissue irritation from frequent handshaking and the use of aspirin, which is taken as part of a standard cardiovascular prevention regimen.” The doctor’s statement continued. “This is a well-known and benign side effect of aspirin therapy.”
Shortly before the release of Dr. Barbabella’s memo, Karoline Leavitt delivered the same information to reporters and emphasized, “The president remains in excellent health,” according NBC News.
And his physical examination that was released three months ago said the same thing.