My advice; Be honest (tell the boss you feel better that way) and don't care beyond that.
I wear jeans + T-Shirt and a Hoodie 99% of the time.
I had a super busy week once and forgot to wash any jeans, so I put on trainer pants. Colleagues (even the boss) made fun of me few times during that day. I jokingly explained to them that I forgot to do basics in my life and everyone was happy. I don't think anyone felt any emotions regarding my clothes beyond that few secs we were chatting. I think it will be the same in your case if they are at least a bit professional.
I wear jeans + T-Shirt and a Hoodie 99% of the time. I had a super busy week once and forgot to wash any jeans, so I put on trainer pants. Colleagues (even the boss) made fun of me few times during that day. I jokingly explained to them that I forgot to do basics in my life and everyone was happy. I don't think anyone felt any emotions regarding my clothes beyond that few secs we were chatting. I think it will be the same in your case if they are at least a bit professional.