There are no true viruses for Android. There is malware, i.e. malicious apps, but you need to actually install it - it's can't just "infect" the machine because you visit a site.
Malware is very rare in the Play Store, though very common in piracy sites (anywhere that offers paid apps as free downloads). So as long as you've been careful with where you load apps from you have little to worry about.
If you are still worried, there are free security apps, such as Avast!, which you can load from the Play Store and use to scan the phone. No security software is perfect, so your best defence is still to be careful about what you install.