Partner feels IUD?

I got the IUD on Monday and my partner and I waited 3 days as recommended to have sex - but since then my partner has told me during sex he feels something ‘spiky’ (which we assume are the strings of the IUD!) I really don’t want him to be hurting, is there something wrong or do we just have to wait for the strings to soften?

Wondering if anyone else has this issue?

We love having properly deep sex so it’s kind of a bummer, please help a gal out!!