Hello, @Muhammad Shoaib,
Please copy and paste the below given CSS code to XStore >> Theme Settings >> Theme Custom CSS >> Global CSS and check back to your site after removing the cache, It will bold the price text on your site.
span.woocommerce-Price-amount.amount {
font-weight: 900 !important;
}
.single-product p.price {
font-weight: 900 !important;
}
Regards 8Themes Team.