Sharing pictures or selfies with someone you don't know is NEVER a good idea.
The person may seem really friendly and interested in you but sometimes they are not who they say they are and may not really be friendly.
If anyone asks you for a picture in an online chat, you should think about who they are and why they want a picture. If you don't know them in person or are friends with them in real life, you shouldn't send any pictures.
Now that you've made a good decision, you should tell a responsible adult what happened. There is nothing to be embarrassed about. You could tell you Mum, Dad or Guardian.
You can always contact the police on 101 if you are concerned or worried about anything that has happened in an online setting.
In an emergency ALWAYS dial 999.