Laptop fans suddenly loud (even shortly after a boot)?

When I got my laptop, my fans were never that loud however, I normally have these bottle caps I place under it for optimal airflow. Today, my brother removed them without my knowledge and placed it back on the perfectly flat table surface where it was under intense gaming for a few hours. I only noticed this when one of my fans suddenly got very loud. Since then I shut it down, reset the laptop onto the bottle caps, and then let it all cool down. Now, even at startup,the fans are noticeable louder and I don't know what that means or what to do. Does anyone know what I should do or have a guess as to why this is happening?