Is the pace swing dramatic? Like 6:00 pace for one mile and 8:00 pace the next mile?
If so, just try going slower, somewhere in the middle or on the slower side. Focus on being relaxed, as if you could have a conversation with somebody (even better, find a friend to run with and talk to them). Talk to yourself out loud if you need to.
Or is it like 6:30 one mile and 7:00 the next one.
If so, that's not really a big deal. Could just chalk it up to running over some hills or something. Don't worry about it
Consistent pace is not really that important unless you are doing a workout or a race. If you are just out on a training run, it's probably fine as long as it is not exhausting you. Are you new to running, or have you been running for several years?