Am I (21f) being sensitive after my boyfriend (26m) made a money joke ?

My boyfriend (26m) and I (21f) just went to the shop and I asked if he could pay because we were on our way back from work and my phone was on 3 percent and didn’t have my cards on me. In front of the shopkeeper at the till he turns around and jokes saying “I should of never shown you my payslip” and now is acting cold and distant and not seeing how it could have made me feel. How should I go about this?