Your credit report won’t be affected by your decision to be a guarantor, except in the case where you have to cover the loanee’s repayments.
In this scenario, both timely and missed repayments will be logged on your credit report as if you applied for the loan.
Provided this doesn’t happen, your ability to be approved for other types of credit won’t be affected by being a guarantor.
It’s only during mortgage applications that being a guarantor will be taken into account by lenders.