To persistently prod or needle someone until they confess something or speak their mind. It also involves using provocative or persuasive language to get a rise out of someone, making them angry at you, a situation, or someone else.
I was at it all day. I pinché him, I pinché him, until he finally told me the truth.
To coax, wheedle, or peer-pressure someone into doing something they were refusing to do or hesitant about.
Someone does not want to drink, take photos, or go out, but another person manages to sonsacar them and get them to do everything they did not want to do.