What should I do if my headphones don't go into my iPhone 4s
If none of the headphones you try (you should try different sets) can physically fit into the port, then there is probably something lodged down in the port. Shine a light down it and see if you can find anything. If you have repeatedly tried to dislodge whatever may be there but seem unable to get it out, go to an Apple store and see what they have to say about it.