Any time you have to enter your PIN you are putting yourself at risk of someone seeing it. It could even be a fake PIN pad, so covering with your other hand won't help. If they can then steal the card from you, they can spend freely at merchants and withdraw cash at any ATM up to 2X your daily limit (once at 23:59, once at 00:01).

If they steal your card without a PIN, they can use it contactlessly only for small transactions up to the contactless limit, and only for a limited amount before the card will stop working (if you make too many contactless transactions in a row, the bank will refuse one and demand a PIN transaction). (At least in the UK), you are not liable for the contactless transactions made after your card was stolen.