callous, callus

Callous or callous means cold, unfeeling, or having no sympathy or understanding for other people--
His callous disregard for the consequences of his actions was considered an aggravating circumstance.
That was a callous remark!

Callus or callus ( rhymes with callous ) means a thickened spot on the skin where someone has used a tool or implement repeatedly--
Many people have a pencil callus on their right middle finger.
His hand had a callus from wielding a hammer for years.

Now that you know that, you can say--
"He sneered when he saw a callus on someone's hand, displaying his callous attitude."

 Note--not to be confused with callow, meaning unripe or immature ( of a person )--
"Callow youth" was once a common phrase.
"Try to remember that kind of September when you were a gay and a callow fellow."
Note #2--"Callused" means having calluses, or thickened skin where something has repeatedly rubbed--
His hands were callused and scarred.