In my experience whenever I apply for a loan or credit card account my credit score drops by 5 points from each hard inquiry.
The hard inquiry then stays on your credit report for a period of 2 years but the hard inquiry loses it's affect on your credit score after one year.
Your credit score should return to what it was before or improve after 2 years.
Avoid opening up too many accounts because each hard inquiry that is made will lower your credit score and too many accounts can really lower your credit score to 500 which is a bad score when needing to apply for mortgage or other loans.
Only open up credit cards and take out loans that you need or can pay back on time without missing payments.