Correct spelling, explanation: worsen comes from an Old Saxon word werran, which had the meaning of entangle and was used in reference to a problem that got more difficult. Before the verb worsen appeared, the adjective worse entered the language in the Middle Ages. In modern English, worsen is a verb used in different contexts.

Definition of worsen:
1. verb – when something becomes worse,
If I were you, I wouldn’t say anything as in this case, telling the truth may only worsen the situation.

Collocations with worsen:
Some popular collocations with worsen are: continue to worsen, suddenly worsen, and significantly worsen.
If the problem of global warming continues to worsen, we are going to experience more and more severe weather conditions.
Unfortunately, in the case of any cancer, the condition of a patient may suddenly worsen.
If the company doesn’t increase the production and the sales of new products, our financial situation will significantly worsen.

Incorrect spelling, explanation: the English verb worsen is often associated with worst, which is a superlative form of the adjective bad. The result of that is a common spelling mistake, which is worsten. This form is totally wrong and the only correct form is worsen.