Hi Susan welcome to the community
I'm not an expert but I would say they wouldn't peck at the hole throughout the nesting period, I assume you have Blue Tits checking the box out?, they seem to peck at the hole at the start, I've seen it mentioned where people think they are marking the box as theirs.
One thing you must not do is keep checking the box or they will desert it, unless you can tell both adult birds apart so you can see them change over when incubating I should wait till you might hear the chicks in the box.
Hi Susan and welcome to the community from me too. As Alan says I would imagine the "sometimes obsessive" pecking at the entrance hole should stop once the female starts to lay her eggs but agree that you should steer clear of an active box however tempting it is to peak inside. The female blue tit, as you probably know, builds the nest by herself and she may use feathers from her breast to create a brood patch so maybe that could be a hint she has laid eggs and apart from going out to feed and do the necessary she will spent a lot more time in the box. There is a handy calendar about blue tits HERE giving some timing indications. Good luck and hope you get to see some lovely fluffy blue/yellow chicks in early June.
Forgot to say, if you keep your eye on the box you may see the male blue tit bring the female food (to the box) whilst she's sitting on eggs.
Many thanks to Alan and Hazel. I am not able to see into the nest box so wont be disturbing them. Thanks for the info re looking out for the missing feathers on her breast... I'm so excited as I have had a box in my garden for several years but have not been successful, I think it may have been due to the hole being too large, so my hubby change the front.
Hello Susan, welcome from up at the very top of Scotland, in Caithness. Hope you will have babies in the nest box.