Yes, if you have an excess contribution in 2018 that you will not withdraw in early 2019, then you carry over that excess to 2019. This excess is applied as a "personal" contribution in 2019. This means that you need to make sure that you reduce your 2019 contributions so that the carry over plus your actual 2019 contributions are less than your annual HSA contribution limit.
You will be charged a 6% excise tax on the carryover amount next year.
