Starting a conversation can be hard, especially if you're worried about your child and what they may be feeling. The most important thing is you give your child the opportunity to talk if they want to. It doesn't really matter what topic the conversation starts with - it's about the opportunity it gives you both to talk about feelings and to provide comfort.
Here's some conversation starters:
Lots of parents find it useful when starting a conversation to pick a current topic they know their child would be interested in. This may be a new song that talks about emotions, a magazine with an interesting article in, a film you recently watched together, or a storyline in a soap or tv programme. This places less focus on the child and often leads to natural conversations about feelings. As mentioned above sometimes doing a fun activity together can help too and provides a relaxed and comfortable environment to get the conversation started.