TIFU by giving out the MD’s mobile phone number as my own

This was a mistake that happened a number of months ago, however I have only just realised and I’m mortified.

This is not a long story, but a couple of months ago our company went through a re-branding. I work for an international construction and services company, and the UK division turns over around £500m. A few weeks after the re-branding HR were hassling people about changing their email signatures to the new logos, and in a moment of unrivalled brilliance and ingenuity, I thought to myself - ah the MD will definitely have the newest and best email signature, I will copy and paste his! So I copy his signature, create my new one replacing all the relevant detail with my own (or so I thought).

Fast forward a number of months and I get an email from a subcontractor asking me to give him a call because he can’t get through on my mobile. When I call him back he explains to me that he tried to phone the number at on my email, however when he did he got through to someone called John Smith who sounded agitated and asked him why people kept calling him and asking for me… at that moment I knew with perfect and devastating clarity what I had done. Yup I had changed all the relevant information except the phone number. I had been merrily emailing suppliers, subcontractors, hire companies etc with the MD of the entire companies mobile number at the bottom of my email.

I have obviously now changed this back, but I don’t really know what to do. Like should I email him and explain and apologise? Or just ignore it and never speak of it again. Everyone in my site team thinks it’s hilarious.

TL;DR I copy and pasted the MD’s email signature for my own but didn’t change the phone number. People have been calling the MD for months and asking for me.