If you have a spare spoke, I've found you can use that to thread into the nipple from the rim bed side, and use that to take it out. Also seen people use a cut off shaft of a q-tip
Managed to perform a lucky direct swap on my knackered rim, a DRC ST17 (Open Pro copy) to a wider Campagnolo Montreal 76. Very similar ERD, kept my spokes, easy peezy lemon squeezy.
If you have a spare spoke, I've found you can use that to thread into the nipple from the rim bed side, and use that to take it out. Also seen people use a cut off shaft of a q-tip