Sentense: I have got an appointment with a Doctor at 5pm.

I have got an appointment with a Doctor at 5pm.I think he wont mind if you come along.

Is the above sentence correct?

No, it is not correct.

It should be written like this:

I have got an appointment with a doctor at 5 p.m. I think he won’t mind if you come along.

Better would be:

I have got an appointment with a doctor at 5 p.m. I don’t think he will mind if you come along.