let phone = document.querySelector("#phoneIcon")
phone.addEventListener("click", function() {
  phone.classList.add("phoneIconClick")
  phone.parentNode.removeChild(phone)
})

#aside {
  clear: both;
  float: right;
  margin: 5%;
}

#phoneIcon {
  font-size: 30px;
  border: solid;
  padding: 5px;
  border-radius: 50%;
  position: fixed;
}

.phoneIconClick {
  font-size: 15px;
  border: solid;
  padding: 10px 0px 10px 300px;
  border-radius: 10%;
}

<aside id="aside">
  <span id="phoneIcon"><i class="fas fa-phone"></i></span>
</aside>