There is no issue with your Visa Waiver when you enter by land.  According to [CBP][1] you don't even need ESTA.  So as long as your Waiver clock still has some time on it see [here][2] or [here][3] you should not have an issue.

[1]: https://help.cbp.gov/app/answers/detail/a_id/1258/~/esta---traveling-to-u.s.-by-land
[2]: https://travel.stackexchange.com/questions/42194/land-crossing-to-america-from-mexico-with-esta-90-days-reset?rq=1
[3]: https://travel.stackexchange.com/questions/60819/if-someone-is-visiting-the-us-under-esta-for-90-days-goes-to-mexico-for-another?rq=1