If I have a thyroid problem if I don't take the medican will it hurt me?

Yes. If your thyroid is too low (hypothyroid) & you don't take your meds for a long enough time, eventually you can develop myxedema, which can lead to coma & death. If you have too much thyroid hormone (hyperthyroidism), not keeping it suppressed can lead to palpitations, & ultimately put so much strain on your heart that it fails. So take your meds!
It could kill you. Of course that depends in the severity of the disease. But even mild hypothyroidism increases the risk of heart disease, and mild hyperthyroidism can lead to atrial fibrillation.