Neither here nor there
Definition 1 of 1
Pro Tip 1/3Conversational Tone
Used often in casual talk to express that something isn't worth considering in a situation. 
Who he dated before is neither here nor there; what matters is how he treats you now.
Pro Tip 2/3Subjective Use
Can imply that what's unimportant is a matter of personal opinion, not fact. 
You might dislike her style, but that's neither here nor there regarding her skill.
Pro Tip 3/3Avoid Overuse
Don't rely on this phrase too much; it might seem dismissive if overused. 
Avoid saying a friend's opinion is neither here nor there frequently; it may upset them.