verb
digress
dy-GRESS/daɪˈɡres/
To move away from the main subject when speaking or writing.
The instructor digresses into a fishing story during the bicycle-repair lesson.

Etymology
The pieces picture “stepping aside”: a speaker or writer leaves the main subject as though departing from a path. The verb may have been formed from digression.
In context
I'm going to digress a little bit and touch on a question that I usually ask up front and I didn't this time because I totally forgot to.
More examples
- Please do not digress from the main question.
- She often digresses when telling a story.
- After digressing briefly, he returned to the evidence.
Forms
digress · digresses · digressed · digressing
digression noun — a departure from the main subject