How do I tell my mum about my health condition?

For the last few weeks I've had a swelling in my groin area. Just been to the doctor's and he said it's almost certainly a hernia. I haven't had a scan yet so it's not confirmed but most likely I will need surgery which is only minor. I haven't told my mum yet as I didn't know what it was and didn't want to worry her but I feel bad keeping it a secret and want to mention it to her. I'm not sure how to start the conversation without her panicking. Don't just want to say I've been to the doctor with a lump in my groin I sort of want to ease it to her so she doesn't start panicking before I can fully explain? How do I start the conversation?