You can basically do this in 2 ways either get the pawn’s mesh and add a impulse to the rootbone that is a one time call or add a force to the bone over a tick .
Add Impulse Doc :
no more casting required in newer version of engine but if you are using the old version you have to cast it to primitive component .
YourMEsh->AddImpulse(UpVector*impulseAmount, yourBone , true);
you can still achieve the same result using addforce by calculating the variable force
doc :UPrimitiveComponent::AddForce | Unreal Engine Documentation