I bought the gold necklace for a few days and I felt that my neck was very stabbing. Can I change it?

First of all, you must be sure whether it is caused by the skin, or the necklace caused by a thorn.
The skin is caused by your skin. Just try not to bring. There is no need to change this.
The explanation caused by the necklace is that the burrs are not handled clean when the gold processing is processed. You can scrape the burrs with agate or other hard objects or send them to the merchant you bought for them to deal with it. The second is that it is not pure gold in itself.