Which is the correct option?

Yes, the second option ,the party was really boring, is the right one.

Adjectives ending in -ed and -ing are generally confused. Let’s analyse them a bit further so as to help you avoid making this common mistake. 

 On the one hand, adjectives that end in -ed generally describe how people feel (emotions).

I was so bored in the party that I almost fell asleep. 

 Here, the adjective bored describes the way I felt in the party.

On the other hand, adjectives that end in -ing describe the thing that causes an emotion.

The party was really boring.

In this example, the adjective boring describes the party (what caused me an emotion: to feel bored).