Pinch out Dahlias

Hi, I’ve got some dahlias which are all doing well but the one (Jowey Joshua) which was left in the ground over winter is doing very well, too well?  It’s only the second year I’ve grown dahlias so I have limited knowledge! Should I pinch out the top leggy growth on the photo? It is about 40 inches tall and seems to have grown about 12 inches in the last week.  There are buds on the top of this leggy bit but should I cut them down to the bushy part?  My worry is that the stem is quite thick, about the size of my finger. Is it too thick to cut now? Photo attached.  Many thanks.