Yes, you must have dragged it. I can get something similar, see? If so, move your pointer to the edge of the bar and when it forms a double arrow, drag it back down to the size you want. Very simple.
Not to worry...I fixed it with the "two-headed' arrow and dragged it down... This incident will teach me to lock the task bar, in future.
Also, I had gone looking for a solution in the interim... https://answers.microsoft.com/en-us...h/1644fdfc-196d-4287-97a4-367d9fd95ff1?auth=1
It's been so at least since the XP times so, the only thing you need, it is Your head, mouse and one hand.