When I first got hired at my current company, I temporarily oversaw one of our other market while my co-worker was on maternity leave.

When I first got hired at my current company, I temporarily oversaw one of our other market while my co-worker was on maternity leave. When she returned, I transitioned back to the market I was originally hired for and all has been going well. This afternoon, my Director called and said that my co-worker is pregnant with baby #2, however, this time, she wants to focus on her growing family and has decided to resign by the end of this month. With that said, my Director wants me to oversee both markets *permanently* moving forward. He offered a raise with this additional market responsibility. Overwhelmed with everything, I verbally accepted the new responsibility and raise. Now that I have had some time to process this news, I'm still excited about the opportunity, but I want to go back and for more money as I'm just now realizing the complexities and challenges of running both markets. What is the best way to approach this and ask for a higher salary after I verbally accepted?