.form__name {
position: relative;
}
.form__name::after {
position: absolute;
content: '';
display: block;
height: 45px;
width: 45px;
background-color: red;
top: 0;
right: 0;
}
<form class="form" action="#">
<input class="form__name" type="text" placeholder="Введите свое имя..." />
</form>