New nesting box and fighting cockatiels

[hwood]

we have had a breeding pair of cockatiels for 1 year, the previous owners said they have already laid 3 clutches and 2 were successfully raised. We just attached a nesting box to the cage, and now they have started fighting. Our female-who has always been the docile and quiet one, hardly nipping and never biting-started rushing the male and fighting with him, outspread wings and everything! That was when the box was in the cage, we now have hung it off the outside and now when they see eachother they both rush and are at war. No blood has been drawn, but it has only been 2 days of this and we keep separating them. Should we take the nesting box away or let them work it out and get used to it?