Salesforce provides an out-of-the box setting features which allow you to skip validation rules when converting a lead to contact.
Follow the below steps to skip validation rules when converting a lead:
Step 1) Login in your Sales force account and open the Setup option from Gear icon.
Step 2) Search “lead setting” in “Quick Find” search box.
Step 3) In the “Lead Conversion Settings” section un-check the “Require Validation for Converted Leads” option and click on the Save button to save your changes.