When you apply for a personal loan, your lender will check your credit history. This enquiry will be formally recorded on your file and could cause your credit score to dip slightly. As such, you should always consider every application carefully and only seek credit when you really need it.
The good news is that if you do apply and are approved, your score could actually improve in the long run. By making your repayments in full and on time, you will show that you are financial responsible. This will make you more attractive to lenders and could make it easier to get credit in the future.