Bad situation!!

So I got myself into a tough situation. My co worker asked me today after work if I wanted to go see some local water falls with him. We had talked about nature a little bit and we both know we share actual like for trails, hiking, etc. I married but he does not know this. I don't wear my wedding rings to work because what I do fort job would damage them if I did. He is fairly new at work we so It hasn't come up in conversation that I am married. I feel weird just blurting out randomly that I am married. Anyways, he asked If I want to go to the falls with him after work, he could show me where they are since I am fairly new to the area and Don't know a lot of the area. I said I had something to do tomorrow and then he asked if I could go Saturday. I have something I am doing then too. Then we finally decided on Monday. But I was so nervous and timid, I just said yes even though I wanted to say no. I am such a people pleaser and have a hard time telling people no. I hate that about myself. My husband thinks I should tell him that my husband needs me after work so I can't go. I just so nervous!! I hate getting myself in these situations and I need to be brave to just come out and say I am married! I am just dreading that awkwardness that is going to come because I work with him every day.